Electrochemical cells with a potassium ion selectivity electrode (Na-ISE) as a measuring electrode versus a chloride ion selectivity electrode as a reference electrode (Cl-ISE) were used to investigate the interaction of solute-solute and solute-solvent in the CsCl-saccharide(D-glucose, D-fructose and sucrose)-, water ternary system at 298.15 K. The activity coefficients of CsCl in saccharides aqueous solutions can be determined through the measurements of electromotive force, and the activity coefficients of saccharides in CsCl aqueous solutions can be evaluated in terms of the Scatchard theory. The McMillan-Mayer theory is employed to relate the excess thermodynamic function with a series of interaction parameters of solute in water so as to obtain the pair Gibbs free energy interaction parameters and salting constant. These parameters have been analyzed by using the model of structural interaction, the effect of hydration of hydroxyl of saccharide and the theory of dispersion energy and the stereostructure of saccharides, which indicates that the interactions of these saccharides with CsCl are controlled mostly by the structure and conformation of their molecules in water.